Actually, there's quite a bit of evidence that Santa doesn't exist. For example, the laws of physics show us that reindeer can't fly. We know that nobody lives at the North Pole. People have been there, and the living conditions are, well, not that great. We know that there's no toy factory up there. We know where toys are ACTUALLY made. We know from logic that no one can be at every house in the world delivering presents at the same moment in time… we know that's impossible. Now, I'll grant you all that this evidence could be classified, perhaps, as "indirect"… but it is evidence nonetheless.